Packaging of semiconductor devices in die form has lead to the implementation of various techniques to effect electrical connections to the semiconductor devices as well as to effect paths to dissipate heat. Often, the semiconductor devices are mounted over a multi-layer circuit board (MLB). One type of MLB comprises laminated layers of dielectric material with selectively disposed electrical circuit traces at each layer. Another type of MLB comprises a plurality of layers of ceramic material with selectively disposed electrical circuit traces at each layer. The MLB provides a substrate for a chip carrier comprising a plurality of individual die and enables the “fanning out” of input/output connections to the individual die.
Vias can be provided through the MLB to provide electrical connections to the die, and to provide a path for dissipation of heat generated by the die. Vias in the MLB can also be provided to enable selective electrical interconnection between electrical circuit traces on the MLB.
Efficient dissipation of heat improves the thermal performance of the die, which in turn can provide improved or consistent electrical performance of the die. Effective heat removal from the die through the MLB requires an efficient thermal path with low thermal resistance.
One type of via is substantially hollow and is referred to as a “barrel” via. Another type of via is substantially solid and is referred to as a “filled” via. The die can be connected to the via using a contact pad. Typically, the die is connected to a printed wiring board (PWB) using a wire-bond or using a solder bump. The latter connection is often associated with so-called “flip-chip” packaging.
The use of known vias presents limited efficiency in dissipation of heat from die on MLB. This results from an unacceptably high thermal resistance of the thermal path from the die through the MLB. What is needed, therefore, is a MLB with improved thermal dissipation of heat from dies provided over chip-carrier substrates.